The combination microelectronic mechanical systems (MEMS) and integrated circuits (ICs) allows for the possibility to make any number of micro-sensors, transducers and actuators. Unfortunately, typical methods for making MEMS are incompatible methods used to fabricate ICs. Hence, MEMS and ICs are usually fabricated separately and laboriously combined in subsequent and separate steps.
In addition to the MEMS and ICs processing incompatibilities, MEMS typically require encapsulation, whereby the active portions of the MEMS are sealed within a controlled storage environment. One way to encapsulate the active portions of the MEMS is to provide unique customized packaging structure configured with conductive leads fitted for the MEMS. Alternatively, the MEMS can be formed on a wafer substrate that serves as a bottom portion of the packaging structure. After the MEMS is formed on the wafer, then a matched lid structure is glued or soldered over the active potions of the MEMS to seal the MEMS within the suitable storage environment. For example, Shook describes a method and apparatus for hermetically passivating a MEMS on a semi-conductor substrate in U.S. patent application Ser. No. 09/124,710, and U.S. patent application Ser. No. 08/744,372, filed Jul. 29, 1998 and both entitled METHOD OF AND APPARATUS FOR SEALING A HERMETIC LID TO A SEMICONDUCTOR DIE, the contents of both of which are hereby incorporated by reference.
A grating light valve™ light modulator is one type of optical MEMS that is used to modulate one or more wavelengths of light. A grating light valve™ light modulator comprises a plurality of reflective ribbons which move relative to a second set of ribbon and/or a reference surface to modulate a incident light source. Grating light valve™ light modulators have applications in display, print, optical and electrical device technologies. Examples of a grating light valve™ light modulators and their uses are disclosed in the U.S. Pat. No. 5,311,360, issued to Bloom et al., which is hereby incorporated by reference. More advanced designs and techniques for making grating light valve™ light modulators, also referred to as flat light valves, are described in the U.S. Pat. No. 5,841,579 and the U.S. Pat. No. 5,808,797, both issued to Bloom et al., the contents of which are also both hereby incorporated by reference.
Many of the current processing technologies that are available for the fabrication of MEMS do not provide sufficient throughput, selectively or are incompatible with standard CMOS materials. Further in the case of grating light values current processing often leads to stiction of the movable ribbon structures (a condition whereby the ribbons stick to the substrate) and/or results in the degradation of the reflective coating on the ribbons.
What is needed is a method to make MEMS and other micro-structures utilizing processes that are compatible with standard CMOS material and/or IC wafer processing, and preferably whereby MEMS and ICs are capable of being fabricated on the same wafer chip. Further, what is needed is a method to fabricate MEMS, wherein the active portions of the MEMS are readily encapsulated within a variety of suitable storage environments.